undiagnosed chronic foot pain

I have been to 10 different doctors over the past two years–including a podiatrist, a sports medicine specialist, and an orthopedic surgeon–and have received no firm diagnosis and no pain relief.
The pain began shortly after running a half-marathon in 2011 (I was 20 at the time) and slowly increased in intensity until it reached the debilitating point at which it is now.
The most severe pain seems to be focused at the base of the first toe joint and continue throughout the area between the first and second metatarsals.
It ranges from a sever, sharp pain to a dull ache.
The other location of pain is between the third and fourth metatarsals near the toe joints.
X-rays are normal, MRIs are normal–showing healthly sesamoid bones and no neuromas, bloodwork in normal (no rheumatoid or other autoimmune disorders), and a bone scan shows a slightly increased uptake at the mid-foot joint, but nothing significant.
Activity and direct pressure intensify the pain.
I have custom orthotics with motion control and metatarsal bars/pads which are somewhat helpful, but the pain is still debilitating.
If anyone has any ideas of where I can go from here, they would be greatly appreciated.